A major obstacle in designing an effective ocular drug delivery system is the anatomical challenge presented by the eye. Both in access and available space, the eye is unlike any other organ due to its isolation and compactness. Because of these limitations, ocular drug delivery systems will desirably include, for example, 1) minimally-invasive deployment, 2) sustained drug release on the scale of several months to years (including release of formulation-challenging drugs, such as those with limited aqueous solubility), 3) extremely high biocompatibility, and 4) biodegradation on a time scale similar to release of the entire drug payload. Unfortunately, typical delivery systems generally do not meet one or more of these criteria.
Reverse thermal gels (RTGs) have been proposed to address some of these desired criteria. However, typical reverse thermal gels generally have poor drug-eluting characteristics, which are generally due to high water content of the gels. Although the high level of water contributes to a biocompatibility of the gel, the high water content (typically greater than 90%), causes the gels to suffer from an inability to hinder rapid diffusion of a drug out of the system or gel. As a result, such systems generally have a release period that is at most on the order of days to a couple of weeks. In addition, typical RTG systems are relatively unstable, because the systems are loaded with drugs at concentrations above a solubility level of the drug in order to be clinically relevant.
Accordingly, improved methods, systems, and devices for providing sustained therapeutic agent delivery are desired.